This invention relates to methods for preparing peroxides and monoxides having at least one pentahalosulfur (VI) functional group. The invention further relates to novel pentahalosulfur hypohalites useful in preparing these peroxides and monoxides, and methods of producing the same.
Compounds such as bis-(pentafluorosulfur) peroxide are known to be useful as reagents for introducing an oxypentafluorosulfur group (—OSF5) into an organic molecule, such as a benzene ring, by substitution or oxidative addition. (See, e.g., Claude I. Merrill, et. AI, Some Reactions of Bis-(pentafluorosulfur) Peroxide, Apr. 5, 1963.) The resulting organic compounds having —OSF5 functionality are useful in a wide range of diverse applications such as electronics, pharmaceuticals, and polymers.
For example, bis-(pentafluorosulfur) peroxide can be reacted with benzene to form oxypentafluorosulfanylbenzene, which is useful in the synthesis of liquid crystal compositions for liquid crystal displays (LCDs). In particular, the —OSF5 group of this compound imparts reduced rotational viscosity on the crystal, thereby allowing the crystal to switch faster and, in turn, improving the clarity of the LCD display. Oxypentafluorosulfanylbenzene (a.k.a. pentafluorosulfaoxybenzene) is also useful as a photodecomposable compound due to its ability to etch a silicon dioxide film coated with a fluorine-containing polymer. (See U.S. Pat. No. 3,960,559.)
Bis-(pentafluorosulfur) peroxide is also useful in synthesizing analogs of known medicinal compounds, particularly medicinal compounds comprising one or more trifluoromethyl functional groups (—CF3). In particular, it is believed that substituting an oxypentafluorosulfur group for a trifluoromethyl group on a biologically active compound can improved the compound's efficacy, and in some instances, achieves new biological activity. Examples of analogs of biologically active compounds that can be synthesized with bis-(pentafluorosulfur) peroxide include a derivative of fenfluramine, such as N-ethyl-1-[3-(oxypentafluorosulfanyl)-phenyl]propan-2-amine; a derivative of fluoxetine (Prozac), such as N-methyl-3-phenyl-3-[4-(oxypentafluorosulfanyl)phenoxy]-propan-1-amine; a derivative of trifluralin, such as 2,6-dinitro-N,N-dipropyl-4-(oxypentafluorosulfanyl)aniline; and the like.
In addition, bis-(pentafluorosulfur) peroxide and similar peroxides are useful as initiators for certain polymerization reactions, such as the homopolymerization of tetrafluoroethylene. These peroxides can also form telomers with hexafluoropropene, and other fully fluorinated olefins.
Different synthesis routes have been proposed for bis(pentafluorosulfur) peroxide. For example, Merrill has suggested the catalytic reaction of SF5OF with OSF2 and/or OSF4 at high temperatures and pressures to produce SF5OOSF5 via the path: SOF2+SF5OF→2 SOF4; SOF4+SF5OF→SF5OOSF5. (C. I. Merrill et al., J. Am Chem. Soc. (1961) 83, 298.)
Merrill also describes the decomposition of SF5OF via ultraviolet radiation to produce SF5OOSF5. Id. In particular, Merrill discloses that irradiating SF5OF for three hours with a 350 watt mercury vapor lamp results in a yield of approximately 25%. Merrill notes, however, that longer periods of irradiation fails to increase the yield of peroxide due to the establishment of equilibrium in the reversible reaction: 2 SF5OFSF5OOSF5+F2.
Witucki describes an alternative method wherein SF5Cl is reacted with O2 under ultraviolet radiation to produce SF5OOSF5. (E. F. Witucki, Inorg. Nucl. Chem. Letters (1969) 5, 437. Another method of producing bis-(pentafluorosulfur) peroxide is described in U.S. Pat. No. 3,142,537 (Pass) wherein sulfur tetrafluoride (SF4) is reacted with pentafluorosulfur hypofluorite (SF5OF) in the absence of oxygen.
Notwithstanding the synthesis methods described above, there remains a need for improved methods for producing pentahalogenatedsulfur oxides, such as methods for economically and efficiently producing bis-(pentafluorosulfur) peroxide in high yields. The present invention satisfies the need for such processes.